import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLEncoder;

import org.json.JSONObject;


public class Distance {

	private static final double EARTH_RADIUS = 6378137;
	private static double rad(double d)
	{
	   return d * Math.PI / 180.0;
	}
	
	/**
	 * 根据两点间经纬度坐标（double值），计算两点间距离，单位为米
	 * @param lng1
	 * @param lat1
	 * @param lng2
	 * @param lat2
	 * @return
	 */
	public static double GetDistance(double lng1, double lat1, double lng2, double lat2)
	{
	   double radLat1 = rad(lat1);
	   double radLat2 = rad(lat2);
	   double a = radLat1 - radLat2;
	   double b = rad(lng1) - rad(lng2);
	   double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a/2),2) + 
	    Math.cos(radLat1)*Math.cos(radLat2)*Math.pow(Math.sin(b/2),2)));
	   s = s * EARTH_RADIUS;
	   s = Math.round(s * 10000) / 10000;
	   return s;
	}
	
	
}
